macOS SE | Create LAA Frontend: Host details Actions dropdown, modal, activities

[cdcme]

Related user story

Parent: #37141

Task

Add "Show managed account" to the host Actions dropdown (ADE hosts only), implement the Managed account modal, and add activity item components for global and host-level activity feeds.

Conditions of satisfaction

• "Show managed account" appears/hidden/disabled per the table above
• Correct tooltip for pending and failed/not-enrolled states
• Hidden when MDM enrollment is not ADE (uses isAutomaticDeviceEnrollment)
• Modal shows _fleetadmin username and masked password with copy + reveal
• cacheTime: 0 — password not cached between modal opens
• All four activity types render in the correct feeds (host-level for created/viewed, global for all four)
• yarn test passes for all new components